The invention relates to a product which comprises sorbic acid and at least one bacteriocin and can be used on its own in feedstuffs or mixed with other feedstuff additives in agricultural livestock rearing.
Antibiotics are frequently used to improve performance in the animal feed sector. In some cases, very similar or identical substances are used in human medicine. The use of antibiotics in the animal nutrition sector is suspected in principle of being responsible for the dangers derived from resistant bacteria, which may also endanger human health in the long term. It is therefore necessary to look for products about which there are fewer health doubts for this purpose of use. Thus, in other sectors too there is increasing replacement of substances about which there are physiological and epidemiological health doubts or else which are harmful for the environment, such as, for example, antibiotics, formaldehyde-emitting materials, halogenated substances, and many others, by materials about which there are fewer doubts, for example in human foods, feedstuffs, pet food, silages, pomace or other waste materials from the food industry. The purpose of these materials is, on the one hand, aimed at maintaining the value of the actual product. However, on the other hand, it is also intended to improve the hygienic condition thereof and achieve a longer shelf life.
It is known that sorbic acid can be employed for preserving feedstuffs. Sorbic acid (trans,trans-2,4-hexadienoic acid) is a colorless solid compound which dissolves only slightly in cold water and is used around the world as a preservative. The principle of action is determined by sorbic acid in undissociated form. Sorbic acid therefore displays its best effect in the acidic pH range. Sorbic acid and its salts have a very good microbiostatic, antimycotic action. At the same time, as unsaturated fatty acid, sorbic acid is virtually nontoxic, which has been proven by very extensive data and by the decades of use of this acid in the human food sector, in animal feeds, inter alia.
Besides sorbic acid, other organic acids have also been employed for some years for preserving feedstuffs and for improving feed hygiene. The hygienic quality in particular of feed for young animals must meet special requirements. This is why some organic acids are approved without a limitation on the maximum amount, on the basis of the national legal provisions concerning feedstuffs.
Bacteriocins are specific inhibitors which are secreted by microorganisms and are lethal for other microorganismsxe2x80x94principally bacteria. Bacteriocins are peptides, polypeptides, proteins or substances which have at least proteinogenic structures and are composed of amino acids. It is moreover possible for these bacteriocins which are composed of amino acids also to contain unusual amino acids such as, for example, lanthionine or xcex2-methyllanthionine. For example, pediocin L50 contains other modified amino acids (L. M. Cintas et al., xe2x80x9cIsolation and Characterization of Pediocin L50, a New Bacteriocin from Pediococcus acidilactici with a Broad Inhibitory Spectrumxe2x80x9d, Applied and Environmental Microbiology, Jul. 1995, pages 2643-2648).
Microorganisms which produce bacteriocin frequently occur naturally, for example in milk and dairy products (cf. for example, E. Rodriguez et al., xe2x80x9cDiversity of bacteriocins produced by lactic acid bacteria isolated from raw milkxe2x80x9d, International Dairy Journal 10 (2000) 7-15). Such microorganisms are moreover continually being isolated from other foodstuffs such as meat and meat products (cf. for example, Food Science and Technology International (1998) 4, 141-158).
The microorganisms which secrete bacteriocins have often already been used for several centuriesxe2x80x94often unknowinglyxe2x80x94for producing foodstuffs in that the bacteria which are intentionally added as so-called protective cultures inhibit, by their secretion products, other bacteria which cause spoilage, are toxic, unwanted or hazardous in other ways. A well-known bacteriocin is nisin. This is produced commercially and has also been employed for some years as foodstuff additive against certain microorganisms which cause so-called xe2x80x9clate blowingxe2x80x9d in cheese.
The fundamental disadvantage of using bacteriocins is that they are active only against certain groups of microorganisms, in particular against close relatives. In addition, bacteriocins are unstable in the foodstuff and decompose after a certain time, so that no activity is available any longer.
The other organic acids known as addition to feedstuffs have the disadvantage that some of them are volatile, have unpleasant odors and, in addition, corrosive effects. The performance-improving effects which can be achieved with them are associated with considerable disadvantages in handling.
The object accordingly was to provide a stable addition which is easy to handle, has a preservative effect and improves performance but does not have these disadvantages.
This object is achieved by a product (composition) which comprises sorbic acid and at least one bacteriocin. The bacteriocin(s) may be employed as such but it is also perfectly possible to employ live or dead microorganisms which produce or contain these bacteriocins. It is preferred to use bacteriocin-producing microorganisms which occur naturally, for example in dairy or meat products. Microorganisms to be employed according to the invention are only those which produce bacteriocins. The table detailed below contains species of microorganisms which may or may not produce bacteriocins (for example Bacillus cereus); these can accordingly be employed only if they produce bacteriocins. The bacteriocin-producing or -containing microorganisms or the bacteriocins themselves can also be employed in encapsulated form or bound to carriers. It is moreover possible to use products which contain bacteriocins in effective concentrations or detectable amounts. This also includes mixtures of such products, for example with whey proteins or common salt. Available products of this type are, for example ALTA2341 (Quest Biotechnology, Inc., Sarasota, U.S.A.) Microgard (Rhxc3x4ne Poulenc, Courbevois, France).
The bacteriocins/microorganisms mentioned in the following table are preferably employed.
The bacteriocins are obtained by known processes, for example by simple precipitation using ammonium sulfate, gel filtration (Sephadex G-50), cation exchange chromatography (CM-cellulose), RP-HPLC, adsorption/desorption centrifugation, vortex flow filtration or other technically suitable methods (see Parente E. and Ricciardi A., Appl. Microbiol. Biotechnol. 1999, 52, 628-638).
The product of the invention contains from 90.00 to 99.90% by weight, preferably 95.00 to 99.99% by weight, sorbic acid. Percentages by weight are based in this case on the total weight of the product.
The bacteriocin(s) are expediently present in the product of the invention in amounts such that from 2.5 to 50 mg/kg, preferably 5 to 40 mg/kg, in particular 10 to 20 mg/kg, are present in the animal feed. Preparations which contain bacteriocins are added in appropriately higher dosage (if, for example, the preparation contains 2.5% bacteriocin as active substance, then preferably from 400 to 800 mg/kg thereof are employed). If bacteriocin-producing microorganisms or combinations thereof are employed in the products of the invention, these are preferably present in amounts which correspond to about 106 to 1010 microorganisms per g of feedstuff. It is also possible to use spray-dried products for this purpose. The bacteriocin content in the animal feed should in this case likewise be from 2.5 to 50 mg/kg, preferably 5 to 40 mg/kg, in particular 10 to 20 mg/kg.
Carriers which can be used both for the sorbic acid and for the bacteriocin or the microorganisms are organic or inorganic materials. These include, for example, starch and other polysaccharides such as cellulose. To improve dispersion in mixtures with sorbic acid, it is also possible for the bacteriocins to be present in the mixtures in salts such as common salt or mineral salts or else whey powder or other products of milk processing.
A further possibility is for the bacteriocins or the microorganisms to be provided with microcapsules/microspheres in order thus to resist unwanted effects of digestive juices. It is possible in this case for the sorbic acid to be put, separate from the bacteriocins, into the microspheres or else into one of the outer layers of a microcapsule in such a way that sorbic acid is released earlier and leads, for example in the stomach, to a marked reduction in pH, but the bacteriocins are not released until later in the gastrointestinal tract. A mixture of encapsulated bacteriocins and sorbic acid is also possible. Examples suitable for the encapsulation are gelatin, lecithins, stearates, alginates, tragacanth, xanthan, carrageenan, cassia gum, gum arabic, maltodextrins, modified starches, celluloses, mono- and diglycerides of edible fatty acids esterified with organic acids or unesterified, solid triglycerides with, preferably, saturated fatty acids such as tripalmitin, solid fatty acids such as palmitic acid or mixtures thereof.
Employed as carrier and for stabilizing the products are  greater than 0 to 10% by weight, preferably 2.5 to 7.5% by weight (based on the product), of carrier materials, alone or in combination.
The product of the invention is produced by, for example, mechanical mixing of the sorbic acid and bacteriocins, bacteriocin mixtures, preparations which contain bacteriocins, or live or dead microorganisms which have produced bacteriocins. If the product of the invention comprises a carrier, it is expedient for the microorganism extracts, which are liquid where appropriate, initially to be applied to the carrier, expediently in a commercially available tumbler mixer or other conventional mixer, and then for the sorbic acid and the other solid ingredients to be added.
Examples of suitable animal feedstuffs are green fodder, silages, dried green fodder, roots, tubers, fleshy fruits, grains and seeds, brewer""s grains, pomace, brewer""s yeast, distillation residues, milling byproducts, byproducts of the production of sugar and starch and oil production and various food wastes. Feedstuffs of these types may be mixed with certain feedstuff additives (e.g. antioxidants) or mixtures of various substances (e.g. mineral mixes, vitamin mixes) for improvement. Specific feedstuffs are also adapted for particular species and their stage of development. This is the case, for example, in piglet rearing. Prestarter and starter feed are used here. The product of the invention can be added to the animal feedstuff directly or else mixed with other feedstuff additives or else be added via premixes to the actual feedstuff. The product can be admixed dry with the feed, be added before further processing (e.g. extrusion) or be metered in and dispersed in the mixture. An additional possibility is to add the individual ingredients of the product separately to individual ingredients of the feedstuff. It is expedient to use for these purposes product concentrations between 0.25 and 7.5% by weight (based on the feed), preferably 0.75 to 4.0% by weight.
The product can be added as sole additive to the animal feedstuffs, for example for cattle, poultry, rabbit or sheep rearing, particularly preferably to prestarter and starter feeds for piglets, or be used mixed with other feed additives for these stock. Feedstuffs having the product of the invention are moreover suitable as milk replacers for the early weaning of lambs or calves.
Surprisingly, the products of the invention do not show the disadvantages described above. On the contrary, the products show good handling properties. In addition, effective acidification of the feed is achieved. It is moreover possible, surprisingly, for there to be a beneficial effect on the growth performance of young stock even with relatively small amounts of product.
The products of the invention are in a solid state of aggregation. The present invention avoids the problems which otherwise arise with the handling of the liquid acids previously used. The product of the invention is also able to improve the hygienic status in that unwanted organisms and spoilage microbes, which may otherwise consume nutrients present, are suppressed.
It has been found, surprisingly, that a marked improvement in performance in relation to growth rate and feed conversion can be achieved by adding even small amounts of products of the invention in piglet rearing. To ensure a significant nutritional activity, it is expedient to add products of the invention in amounts of from 0.25 to 7.5% by weight, based on the feed, preferably from 0.75 to 4.0% by weight.
The invention is illustrated below by means of examples.